Tilting pad journal bearing

ABSTRACT

This invention relates to journal bearings of the tilting pad type in which a ring of circumferentially spaced bearing pads are disposed in a housing to surround coaxially a rotating shaft, and are capable of tilting in the housing on at least an axis substantially parallel with the shaft.

This invention relates to journal bearings of the tilting pad type inwhich a ring of circumferentially spaced bearing pads are disposed in ahousing to surround coaxially a rotating shaft, and are capable oftilting in the housing on at least an axis substantially parallel withthe shaft.

A number of different arrangements exist by which each of the bearingpads is able to tilt about at least one axis with respect to thehousing. All have the ability to tilt relative to the housing about anaxis extending parallel to the shaft rotation axis and some have theability to tilt relative to the housing about other axes to accommodatemisalignment between the longitudinal axis of the housing and the shaft.

Patent specification GB-A-1397551 discloses a tilting pad journalbearing in which pads are loosely contained in a circumferentialdirection between stops extending radially inwardly from the housing. Inoperation, with a shaft present, the stops prevents the pads from beingdragged in a circumferential direction by the shaft. However, it is alsoarranged that the circumferential separation of the ends of the stops isless than the maximum circumferential length of each pad such that theloosely assembled pads are incapable of falling out radially in theabsence of a shaft. One or more of the stops may be apertured to providea lubricant supply duct and each pad surface adjacent the housing tobear thereon in operation is of a smaller radius of curvature than thehousing to permit the rocking or tilting action of the pad relative tothe housing.

Although such a pad structure is apparently simple it has drawbacks bothin terms of manufacture and operation. Each pad requires to be supportedbetween radially extending pins which act as locating means to preventthe pads from being displaced circumferentially by the rotating shaftand act as pad stops to prevent the inverted pads from falling from thehousing wall when the shaft is removed. The positioning of the pinsbetween each pad puts constraints on pad disposition within a splithousing. Each bearing pad tilts by rolling of cylindrical surfaces, sothat tilting is restricted to rotation about an effective axis parallelto the longitudinal axis of the housing and is unable to tolerate shaftmisalignment. Furthermore, such rolling action is achieved by way of aline contact by which all radial loading on the pad is transferred tothe housing. It is therefore possible for the load concentration toresult in plastic deformation of the bearing pad and for any radial playin the bearing to increase, that is, for the bearing to lose radialstiffness.

GB-A-2180888 discloses a vertically aligned bearing arrangement in whichthe bearing pads do not have to support the vertical loading of a shaftand are able to pivot with respect to the housing about many axes byvirtue of a part-spherical protuberance on each pad. However, such aprotuberance not only increases the complexity of the pad but results ina point contact between the bearing pad and the housing, which is evenmore likely to deform and reduce radial stiffness if used to support aheavy load.

CH-B-558,481 discloses a tilting pad bearing on which each bearing padhas on its radially outer surface an integral part-sphericalprotuberance which rests in a correspondingly curved recess in a panwhose radial position with respect to the housing is adjustable by rams.The pad is complex to manufacture by virtue of the protuberance butbecause the contact between protuberance and pan is on a larger areathan a point or line, there should be improved radial stiffness.However, the part-spherical interface also acts as locating means totransfer circumferential loading due to shaft rotation into the housingand the slight curvature of the pan reacts this in a generally radialdirection which affects the radial loading and thus the effectivestiffness. Furthermore, if and when a shaft is removed, there is nomeans of retaining each bearing pad with respect to it supporting pan sothat assembly and maintenance is difficult. Furthermore, because eachbearing pad protuberance and associated pan rotate in tilting underload, the surfaces must conform as well, notwithstanding lubrication, toavoid fretting which would be the equivalent of plastic deformation as acause of reducing radial stiffness. Thus each bearing pad should bemaintained with a matched pan requiring an extensive and costlyreplacement for each bearing pad as well as the risk of separation ifthe shaft is removed.

U.S. Pat. No. 4,714,357 discloses a tilting pad journal bearingarrangement in which a ring of bearing pads line a housing and each padcarries a barrel-shaped protuberance or rocker, attached thereto byscrews, arranged to sit in a cylindrical recess in the housing aboutwhich it pivots. Such an arrangement is cheaper than others because theprotuberance is formed separately from the bearing pad before attachmentand the barrel-shaping enables it to rock or tilt about a second axis.However, this arrangement is still considered to have drawbacks. Theload on each bearing pad is transferred to the housing by way of a linecontact between the rocker and recess, which by way of loadconcentration due to weight or transferring rotational forces may leadto deformation and reduction in radial stiffness. Furthermore, rotationabout the longitudinal axis of the recess is by relative rotation of therocker and recess surfaces, so that unless they are prepared to the samedegree of curvature (and undamaged by deformation) fretting can occurand loss of stiffness. To this end, each rocker and recess pair must bekept together, but as each rocker is freely removable with its attachedbearing pad, and has to be for the radial clearance defining shims to beinserted between them, assembly and manufacture is time-consuming andcomplicated if mistake in assembly is to be avoided.

Having regard to the above examples, it is an object of the presentinvention to provide a tilting pad journal bearing arrangement having asimple and cost effective bearing pad structure permitting improvedbearing stiffness and pad replacement procedures which avoidcompromising bearing performance.

According to the present invention a journal bearing arrangementcomprises (1) an annular housing arranged operatively to surround arotatable shaft, (2) a ring of arcuate bearing pads lining the housingat positions spaced from each other in a circumferential direction abouta longitudinal axis of the housing, each pad having a radially outerface including a mounting surface, and being capable of tiltingindependently of the others about at least a primary tilt axis extendingparallel to the longitudinal axis, and (3) associated individually witheach pad position, pad mounting means comprising (i) a recess, fixedwith respect to the housing, having at least in a cross-sectional planeperpendicular to the primary tilt axis, a surface forming part of acircle centred on the primary tilt axis, (ii) a platform body having acurved supported surface, supported within the recess for rotationrelative to the recess about said primary tilt axis, and a supportingsurface co-operable with the mounting surface of the bearing pad at thatposition, and (iii) spigot and socket locating means extending betweenthe platform body and pad in the direction of a locating axis to inhibitdisplacement of the pad with respect to the platform body in acircumferential direction about the shaft rotation axis, the arrangementhaving the locating means arranged to permit displacement of the bearingpad with respect to the platform body along the locating axis, andfurther including pad stop means, operable to limit displacement of thepad along the locating axis to less than the spigots length of thelocating means, and restraint means extending from the platform body byway of the recess and housing to permit rotational motion of theplatform body about said tilt axis by sliding relative to the recesssurface but prevent radial dissociation of the body from the recess.

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross sectional elevation through a journalbearing arrangement in accordance with the present invention showing,for each bearing pad, pad mounting means,

FIG. 2 is sectional radial elevation of the arrangement of FIG. 1, alongthe line II--II thereof through a single bearing pad and pad mountingmeans, shown in relation to a shaft.

FIG. 3 is a schematic cross-sectional elevation through a section of analternative form of bearing according to the invention illustrating adifferent form of locating means, and

FIG. 4 is a schematic cross-sectional elevation, through yet anotherform of bearing according to the invention, illustrating both adifferent form of restraint and locating means and different form of padstop means.

Referring to FIGS. 1 and 2 a shaft 10 has a longitudinal rotation axis11 about which it is rotatable. A journal bearing arrangement 12comprises an annular housing 13 arranged operatively to surround theshaft, having a longitudinal axis 14 nominally coincident with shaftrotation axis 11.

For illustration and clarity of description, the right hand side of FIG.1 is shown with a shaft 10 in place and the left hand side without theshaft. Furthermore, although the bearing arrangement existsindependently of a shaft with which it is intended to work, thedimensions and other parameters of such a shaft influence thearrangement.

The housing 13 comprises two semi-cylindrical housing parts 13₁, and 13₂joined at interfaces 13₁ ' and 13₂ '.

The housing is lined internally by a ring of n arcuate bearing pads 15₁-15_(n) at respective positions 16₁ -16_(n) spaced from each other in acircumferential direction about axis 14. An even number of pads aredisposed in diametrically opposite pairs, with a whole number of padsbeing contained within each housing part. As shown, there are four pads15₁ -15₄ at locations 16₁ -16₄.

Associated with each pad position 16₁ -16₄ is individual pad mountingmeans 17₁ -17₄, disposed at 90° intervals about the housing but notnecessarily centrally disposed with respect to each associated bearingpad.

The bearing pads and associated mounting means are essentially identicalat each position and for convenience and clarity, description of eachbearing pad, such as 15₁ and mounting means 17₁ within one housing part12₁ will omit subscripts except where context dictates.

Each arcuate pad 15 has a cylindrically concave radially inner face 18,corresponding to the curvature of the shaft which it supports, and aconvex radially outer face 19 including a mounting surface 20 by whichit is supported with respect to the housing by the mounting means 17such that in operation the pad is capable of tilting independently ofthe other pads about at least a primary tilt axis 21 extendingsubstantially parallel to the shaft rotation axis.

The bearing pad mounting means 17 comprises a recess 22, platform body23 disposed in the recess and spigot and socket locating means 24 whichextends between the platform body and bearing pad to inhibitdisplacement of the pad with respect to the platform body in acircumferential direction about the longitudinal axis when the shaft isin motion.

The recess 22 is fixed with respect to the housing and has, in across-sectional plane perpendicular to the primary tilt axis 21, asurface 25 forming part of a circle centred on that tilt axis. Therecess is similarly curved about a secondary tilt axis 26, orthogonal toand intersecting the primary tilt axis, the surface 25 being defined bypart of a spherical surface. The recess 22, although it may be formeddirectly into the wall of the housing, is preferably defined in adiscrete recess member 27 disposed in a cavity 28 in the housing andsecured thereto by screws 29.

The platform body 23 has a curved supported surface 31 by which it issupported in the recess for rotation relative to the recess about eachtilt axis. The supported surface 31 corresponds in curvature to therecess and the platform body is supported by contact with substantiallythe whole area of the recess, that is, is defined by part of a sphericalsurface. To this end, to ensure uniform distribution of load across thesurfaces without irregularities leading to stress concentrations andplastic deformation and/or fretting, the surfaces 25 and 31 are machinedand/or otherwise manufactured as a matched pair.

In at least such cross-sectional plane perpendicular to the primary tiltaxis the supported surface of the platform body is defined by asemi-circle, and conveniently this is repeated for all cross-sectionalplanes so that the supported surface is hemispherical.

A supporting surface 32 of the platform body, defined betweendiametrically opposite sides of the semi-circle, is co-operable with themounting surface 20 of the bearing pad. For convenience and costeffective manufacture, both the supporting surface 32 of the body andthe mounting surface 20 of the pad are machined flat so that the load isspread uniformly to mitigate stress concentration and possible plasticdeformation. It will be seen that each tilt axis associated with themounting means and pad lies in the plane of the supporting surface.

Shim means 35 disposable between the recess member 27 and base ofhousing cavity 28 enables the radial position of the supporting surface32, and therefore the bearing pad surface 18, to be accurately set. Inparticular, by having the locations of the respective mounting meansdiametrically opposite in pairs, the separation of the bearing surfacesof the associated bearing pads (of known thickness) may be accuratelyset to the diameter of the shaft with which to be used by setting thediametrical separation of each opposite pair of supporting surfaces byway of the shim means with the bearing pads and shaft not in place.

The locating means 24 comprises a spigot member 40 carried by theplatform body and extending from the supporting surface 32 in thedirection of a locating axis 41 perpendicular to the supporting surfaceand, in normal disposition, substantially radially with respect to thehousing axis. The locating means further comprises a complementarylocating socket 42 defined in the mounting surface of the bearing padand in which the spigot member forms a sliding fit.

The locating means 24 serves not only to inhibit circumferentialdisplacement of the pad in operation but is arranged to act with padstop means 45, as illustrated for pad 15₂ and described fullyhereinafter, to hold the pad radially in relation to the platform bodyto prevent a bearing pad from becoming inadvertently separated from itsmounting means in the absence of the shaft, whilst permitting readilythe deliberate removal and replacement of a bearing pad withoutupsetting the positional set up or matching surfaces of the pad mountingmeans.

Further associated with each mounting means 17 is restraint means, showngenerally at 50, which extends from the platform body 23, by way of therecess 22 and housing 13 to permit rotational motion of the body abouteach tilt axis by sliding relative to the recess surface but preventradial dissociation of the body from the recess.

Restraint means 50 comprises an elongate restraint member 51 restrainedby the platform body from moving relative thereto towards the recess andhaving a shank 52. Through-aperture 53 of substantially the samecross-sectional dimensions as the shank extends in the platform body ina direction passing through the primary tilt axis and by way of shoulder54 to a wider depression 55 in the supporting surface 32. The shank 52,extends along the aperture 53 and is a sliding fit therein, so as to berestrained from motion other than lengthwise, and includes anenlargement of cross-section 56, conveniently integral with the shank,which is operable by abutment with the shoulder to restrain the memberfrom egress from the aperture 53 towards the recess. The shank 52extends from the body by way of a clearance hole 57 in the recess memberand the housing supporting the recess member to an enlarged flangeportion 58 of the restraint member disposed, with a small clearance fromthe housing, to permit limited displacement of the supported platformbody and restraint member relative to the recess surface 25.

The flange portion 58 is conveniently provided by a lock-nut arrangement59 disposed on a threaded end portion of the shank.

Furthermore, resilient means 60, such as a light spring carried on theshank or spring washer, may be employed to bias the restraint memberaxially with respect to the platform body to urge the latter intocontact with the recess.

As the axis of the restraint member passes through the tilt axis and isin line with the locating axis 41, the spigot member 40 is convenientlyformed by an extension of the restraint member, in particular saidenlargement 56 in cross-section formed integrally with the shank.

It will be appreciated that if and when a housing part is inverted, asshown for part 13₁, in the absence of a shaft the restraint means (asshown exaggerated for 50₂ of mounting means 17₂) permits a smalldisplacement of the platform body and the spigot member of the locatingmeans inwardly of the housing to the extent only of the limitedlongitudinal movement of the restraint member necessary to permit theplatform body to pivot within the recess. Such displacement, althoughaffecting a small separation between the matched surfaces of the bodyand recess, prevents the body from dissociation from its recess with theattendant risk of the correct pair not being re-matched and/or damage tothe surfaces.

Restraint of the locating means with the platform body, in particularspigot member 40, permits the locating means to be employed not only toinhibit circumferential displacement of the bearing pad with a shaft inoperation but also as a simple and convenient way of mounting thesimplified bearing pad in the absence of a shaft.

The simple spigot member extends along the locating axis 41 in agenerally radial direction for a distance above the platform bodysupporting surface that is sufficient for the interface between spigotmember and locating socket to transfer circumferential forces inoperation and is a sliding fit in the locating socket of a bearing padsuch that the bearing pad can be lifted (15₁, 15₄) or fall under gravity(15₂, 15₃) in a generally radial direction for the length of the spigotmember before detaching from the associated mounting means.

Pad stop means 45, operable to limit such displacement of the bearingpad along the locating axis to less than the spigot member length,comprises, for each bearing pad, an abutment surface 65 which isdisposed operatively circumferentially displaced from the locating axis41 associated with the pad and adjacent a wall portion, such as the end15' of the pad, inclined with respect to the locating axis. The abutmentsurface is clear of the wall portion when the bearing pad is mounted inits operative position on the supporting surface of the platform bodybut is abutted by the pad as the latter moves generally radially alongthe locating axis and before the spigot member completely exits thelocating socket, thereby restraining the bearing pad from unintentionaldetachment from the mounting means.

To permit intentional detachment of the bearing pad and, of course,installation of a pad, the abutment surface 65 is movable from itsoperative position to an inoperative one at which such abutment isavoided. Such movement may comprise displacing the abutment surfacelongitudinally and/or radially with respect to the housing or rotatingan abutment surface, eccentric with respect to a radial axis about suchaxis.

Conveniently, the abutment surfaces associated with an adjacent pair ofbearing pads in one housing part, are disposed between the end walls ofadjacent pads in the form a collar 66 supported on a boss 67 extendingradially through the housing wall, which boss is conveniently hollow andserves as a lubricating fluid supply duct to the housing.

Notwithstanding the apparent complexity of the mounting means per se thebearing arrangement is able to provide a high performance specificationcost effectively with a reduction in complexity and cost of maintenanceetc. during its lifetime.

It will be appreciated that the radial stiffness of the bearing is afunction of how much clearance exists, or through use comes to exist,between the shaft and housing that is not occupied by a component body;such clearance may exist by virtue of the tolerances of componentsemployed in combination and without means for accurate setting up oradjustment and/or by virtue of changes to effective dimensions ofcomponents in operation due to loads applied thereto, that is,deformation.

It will be appreciated that in terms of radial stiffness, the accuratelymachined flats of the pad mounting surface 20 and platform bodysupporting surface 32 and the accurately finished matched curvedsurfaces 25 and 35 of the body and recess are capable of transferringconsiderable radial loads, notwithstanding tilting of the body underload, with minimal plastic deformation of, and wear on, the load bearingsurfaces. Furthermore, the provision of shim means 35 permits anymanufacturing tolerances to be eliminated, and even for wear on therunning surface 18 of a bearing pad to be compensated for during amaintenance disassembly when the pad is otherwise serviceable.Furthermore, the mounting arrangement permits such setting up by meansof shim means conveniently and in the absence of bearing pad or shaft.

As an additional effect associated with optimal stiffness, the use of ahemispherical (or semi-circular) platform body and a recess which is ofalmost the same extent, except for the clearance hole 57 and the need toprovide clearance between the supported bearing pad the housing, ensuresnot only that the radial load is supported over a maximum area but alsothat circumferential loading due to shaft rotation is also distributedover an interface having a significant radial component so as tominimise the force being reacted by the interface as a radially inwardforce on the bearing pad.

The bearing pads themselves, although mounted to provide tilting andhigh stiffness, are of simple construction as befits a consumable itemwhich may require replacement, requiring only the locating socket andmounting surface 20 to be provided on the radially outer surface of asegment of an otherwise simply-manufactured cylindrical body whoseinternal bore is prepared and plated with bearing metal to the shaftdiameter before being cut into the segments that form the pads.

The bearing pad structure and mounting means is to be contrasted withprior art arrangements, wherein the attainment of high stiffness is notaddressed, which make use of rocking surfaces that make point or linecontacts and are inherently at risk of plastic deformation from loadconcentration, and/or complex pad structures carrying one part of a pairof relatively rotatable surfaces are proposed. In either event, thebearing pad is relatively complex and expensive to manufacture and ifchanged within a housing, replaced or even moved to a different seatposition, affects the stiffness of the bearing by permitting fretting orother deformation to occur at abutting supporting surfaces that are notprepared as a matched pair, the practical requirement therefore being toreplace both pad and seat as a pair.

Incorporating restraint means into each platform means facilitates notonly keeping each recess and platform body as a matched pair andseparate from any bearing pad associated therewith, but also thelocation, both radially and circumferentially, of its associated bearingpad and obviates the necessity of providing wholly separate locatingfeatures, although that may be done out of choice.

Using the generally radially directed restraint means/locating means atthe part of the bearing pad towards its centre, where it is supported onthe mounting means, makes it convenient to employ a split housingwherein each housing half contains the same number of bearing padswithin the confines of the housing and with no requirement for inter-padstops or the like at the sites of the joint interfaces between housinghalves.

The embodiment described above with reference to FIGS. 1 and 2 may bevaried in details other than those outlined in the description withoutdeparting from the invention.

For example, in respect of the locating means, the locating spigot maybe separate from the restraint member and anchored in the platform bodywith further spigot members, as shown at 140 in FIG. 3, displaced fromthe locating axis 141 with correspondingly aligned locating sockets 142in the bearing pad. Such spigot member or members could of course beprovided by projection(s) integral with the platform body.Alternatively, although it may detract from the simple pad mountingsurface any spigot member may extend from the pad mounting surface andlocate in a corresponding locating socket in the supporting surface ofthe platform body.

In respect of the restraint means, it will be understood that therestraint member enlargement 56 is prevented by shoulder 54 from fallingfrom the arrangement should the flange portion 58 be removed or shakenloose due to vibration and to this end, an enlargement 56 integral withthe shank portion 52 provides maximum security. It will be appreciated,however, that other forms of enlargement may be provided, such as aninterference fit washer or a nut 56' threaded onto an end of the shank,as shown in FIG. 3; such a nut may, as shown ghosted, take the form of aspigot member of the locating means. The interface between enlargement56 and shank 52 may be locked in some way prior to insertion of themember into body recess 55 and/or a cap 51' may be provided to ensurethe shank cannot leave the housing and detract from inadvertent removal.

If the elongate restraint member is to comprise separate shank 52 andenlargement 56, the shank member 52 and flange 58 may instead beprovided by a unitary body, namely a bolt on which the flange 58 forms ahead.

As an alternative to using such a bolt and separate enlargement 56, FIG.4 illustrates a restraint member 151 which engages with a threadedaperture 153 in the platform body, possibly with some provision toprevent egress due to operational vibrations, such as thread locking ora cap 151' to limit its separation from the housing. Such form ofrestraint member may extend to provide an integral locating means spigotmember 240.

Such a restraint member with integral spigot member may be rotated todisplace it axially with respect to the platform body withoutdisengaging therefrom to shorten the effective length of the spigotmember and permit removal and replacement of the bearing pad withoutrequiring displacement of the pad stop abutment means.

FIG. 4 also illustrates an alternative form of pad stop in which thebearing pad has an aperture 115, similar to the locating socket butdisplaced therefrom, into which a pad stop 145 extends such that theaperture wall 115' is what contacts the abutment surface 165 of the padstop rather than pad end wall 15'.

It will be appreciated that whilst a part-spherical recess and platformbody surface permit tilting of the pad orthogonal to the shaft axis toaccommodate tilting of the shaft axis with respect to the housing axis,it is only in relation to tilting about the primary tilt axis thatsignificant lateral forces have to be transmitted that benefit from anear-semi-circular shape. The recess and/or platform body may thereforebe truncated in the direction of the primary tilt axis, as indicated bydotted lines 25' in FIG. 2, although uniformly spherical surfaces arepreferable from a manufacturing standpoint.

It will be appreciated that by enabling the platform body to rotateabout an axis other than the primary axis, such that the primary axisitself can rotate with respect to the longitudinal axis of the housing,the platform body supporting surface and bearing pad can remain parallelto the axes of the shaft if the shaft is inclined with respect to thelongitudinal axis of the housing. However, if there is certainty thatthe axes are parallel or the extent of any divergence is known andfixed, then the primary tilt axis may be defined in relation to theshaft by way of reference to the longitudinal axis of the housing andhaving the recess and platform body provided with matching cylindricallycurved surfaces.

As indicated above, the shim means 35 may be omitted if desired or therecess may be formed directly within the housing wall.

Where shim means are provided to enable adjustment of the radialposition of each recess member/platform body, the longitudinal axes ofshaft and housing are assumed parallel and a split housing is employed,it will be appreciated that instead of setting radial positions byreference to the distance separating opposing platform bodies, they maybe set by reference to a datum surface extending between the housingjoint interfaces 13₁ ' and 13₂ ' and passing through the longitudinalaxis 14.

The mounting surface 20 of the bearing pad and supporting surface 32 ofthe platform body are required to complement each other to transfer loadwithout deformation and, as the pad and platform body are not providedas a matched pair, it is important that the surfaces can be properlydefined in separate operations. The preferred manufacture is thus offlat surfaces but it will be appreciated that any complementary shapecapable of separate and repeatable manufacture may be used.

For example, the radially outer surface 19 of each arcuate pad 15 may beformed to the same radius of curvature as the internal wall of theassociated housing part including the mounting surface 20. Duringmanufacture each bearing pad mounting means (FIGS. 1 and 2) may bedisposed with respect to the housing part in a temporary fashion withoutshim means 35 and with the locating means 24 replaced by a screw or boltarrangement which holds the platform body 23 tightly within its recess.The radially inner wall of the housing is then machined to the desiredcylindrical dimensions along with the supporting surface 32 of theplatform body. Thereafter the mounting means is reassembled as describedabove and the curved mounting surface 20 bears uniformly on thecorrespondingly curved supporting surface 32.

As described above, the platform body and recess member 27 areconveniently formed of a suitable load bearing and workable metal whichcan not only withstand the operational loading but also themanufacturing process; conveniently both parts are formed of steel,notwithstanding the requirement to lubricate the surface 25 inoperation. However, if desired, the platform body may be made of asintered metal matrix loaded with a dry lubricant, which materialpermits any asperities of initial manufacture to be mitigated bybedding-in with respect to a recess of more wear-resistant material.Such material may not only reduce the manufacturing processes requiredto get a matched pair of surfaces but also mitigate lubrication effort.Such material is available commercially from Glacier GmbH-Deva Werke,Stadtellendorf, Germany.

There may be other than four bearing pads and also there may be an oddnumber of bearing pads in an appropriate housing configuration.

We claim:
 1. A journal bearing arrangement for use with a shaft having arotation axis which the shaft is rotatable, the arrangementcomprising(1) an annular housing having a longitudinal axis arrangedoperatively to surround a said shaft with which used, (2) a ring ofarcuate bearing pads lining the housing at positions spaced from eachother in a circumferential direction about said longitudinal axis of thehousing, each pad having a radially outer face including a mountingsurface and being capable of tilting independently of the others aboutat least a primary tilt axis extending substantially parallel to theshaft rotation axis, and (3) associated individually with each padposition, pad mounting means comprising(i) a recess, fixed with respectto the housing, having at least in a cross-sectional plane perpendicularto the primary tilt axis, a surface forming part of a circle centred onthe primary tilt axis, (ii) a platform body having a curved supportedsurface, supported within the recess for rotation relative to the recessabout said primary tilt axis, and a supporting surface co-operable withthe mounting surface of the bearing pad at that position, (iii) spigotand socket locating means extending between the platform body and pad inthe direction of a locating axis to inhibit displacement of the pad withrespect to the platform body in a circumferential direction about theshaft rotation axis but to permit displacement of the bearing pad withrespect to the platform body along the locating axis, (iv) pad stopmeans, operable to limit displacement of the pad along the locating axisto less than the spigot length of the locating means, and (v) restraintmeans extending from the platform body by way of the recess and housingto permit rotational motion of the platform body about said tilt axis bysliding relative to the recess surface but prevent radial dissociationof the body from the recess.
 2. An arrangement as claimed in claim 1 inwhich the restraint means comprises an elongate restraint memberrestrained by the platform body from moving relative thereto towards therecess and having a shank portion extending by way of a clearance holein the recess and housing to an enlarged flange portion of the memberdisposed to permit limited displacement of the supported platform bodyand restraint member relative to the recess surface.
 3. An arrangementas claimed in claim 2 in which said shank portion extends in saidplatform body along a direction passing through said primary tilt axis.4. An arrangement as claimed in claim 2 in which the locating meanscomprises a substantially radially directed locating socket in themounting surface of the bearing pad and a spigot member, formed by anextension of said restraint member extending from the supporting surfaceand forming a sliding fit in said locating socket.
 5. An arrangement asclaimed in claim 1 in which the locating means comprises at least onesubstantially radially directed locating socket in the mounting surfaceof the bearing pad and a corresponding number of spigot members, eachcarried by the platform body, extending from the supporting surface andeach forming a sliding fit in a corresponding locating socket.
 6. Anarrangement as claimed in claim 1 in which the pad stop means comprises,for each bearing pad, an abutment surface, operatively disposedcircumferentially displaced from the locating axis and adjacent a wallportion of the pad inclined with respect to each locating socket, to beabutted by, and restrain, said wall portion in response to displacementof said bearing pad from the platform along said locating axis and theabutment surface is movable from an operative disposition to permitintentional separation and engagement of the locating means betweenbearing pad and platform body.
 7. An arrangement as claimed in claim 1in which the supported surface of the platform body corresponds incurvature to the recess and the platform body is supported by contactwith substantially the whole area of the recess.
 8. An arrangement asclaimed in claim 1 in which the supported surface of the platform bodyis defined in at least said cross-sectional plane by a semi-circle withsaid supporting surface being defined between diametrically oppositesides of said semi-circle.
 9. An arrangement as claimed in claim 1 inwhich the recess and the platform body exhibit curvature about, and saidplatform body is tiltable with respect to the recess about, at least asecondary tilt axis orthogonal to the primary tilt axis.
 10. Anarrangement as claimed in claim 9 in which the recess and supportedsurface of the platform body are defined by parts of spherical surfaces.11. An arrangement as claimed in claim 1 in which each recess is definedin a discrete recess member disposed in, and secured to, the housing.12. An arrangement as claimed in claim 1 in which there is an evennumber of pad locations and each said platform body supporting surfacediametrically faces another in the housing.